The widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball device, or the like. With the progress of the times, a touch pad has been introduced into the market. By directly using the user's fingers or using a touch pen to operate the touch pad, the computer system or other appropriate electronic device can be correspondingly controlled.
The subject of the present disclosure is related to a touch pad. Nowadays, the commercially available touch pads are classified into several types, including a resistive touch pad, an acoustic wave touch pad, an infrared touch pad and a capacitive touch pad. The operating principles of these touch pads will be shortly illustrated. When a pressing object (e.g. the user's finger) is placed on the resistive touch pad, a voltage change is generated and the pressing position is recognized according to the voltage change. Moreover, acoustic waves pass over the surface of the acoustic wave touch pad. By touching the surface of the acoustic wave touch pad, the travelling path of the acoustic wave is blocked by the pressing object and thus the position of the pressing point is recognized. The operating principles of the infrared touch pad are similar to those of the acoustic wave touch pad. That is, infrared rays pass over the surface of the infrared touch pad. By touching the surface of the infrared touch pad, the travelling path of the infrared rays is blocked by the pressing object and thus the position of the pressing point is recognized. When the user's finger is contacted with the capacitive touch pad, the capacitance value of the touch point of the capacitive touch pad is subjected to a change. According to the change of the capacitance value, the position of the touch point is recognized.
Regardless of which touch pad is selected, it is necessary to install plural X-axis sensing lines and plural Y-axis sensing lines in the touch pad for detection. The plural X-axis sensing lines and plural Y-axis sensing lines intersect with each other to define plural switches. That is, one switch is defined by one X-axis sensing line and one Y-axis sensing line. When a touching action on the touch pad with the user's finger or the touch pen is detected, the corresponding switch is triggered to generate a touch signal. Generally, as the number of the sensing lines increases, the detecting precision increases. However, the increased number of the sensing lines increases the fabricating cost of the touch pad.
Therefore, there is a need of providing an input device with high precision and low fabricating cost.